The use of a capacitance transducer in an electronic balance is well known in the art. The combination of a parallelogram linkage with a capacitance transducer is also well known in the art. A parallelogram linkage is particularly suited for use with the capacitance transducer inasmuch as the parallelogram linkage enables the plates of the capacitor to be maintained parallel to one another as the parallelogram and linkage is deflected.
U.S. Pat. No. 4,344,496 discloses an integral parallelogram load receiver having a parallelogram and a capacitance transducer. FIG. 1 of this patent discloses a circular device having four constrictions which form the hinges of a deformable parallelogram. As the parallelogram is deformed, the capacitance plates 40 and 44 provide a capacitance value that is inversely proportional to the spacing of the capacitance plates. The resilient spring for the device which supports the load to be weighed is formed by the constrictions 22, 24, 26, and 28.
U.S Pat. No. 2,793,026 discloses a spring balance for rapid continuous dosing or controlling that is suitable for process control applications. A pair of parallelogram linkages are provided to compensate for vibration of the supporting structure. The capacitance plates 6, 7 define an electronic transducer measuring the loads supported by pan 11. An adjustable coil spring 8 is used to support the parallelogram, and to offset the load to be measured.
U.S. Pat. No. 3,701,009 discloses in FIG. 4 an electromechanical transducer using a modified parallelogram linkage wherein the spring arms 95 define two sides of the parallelogram, and provide a resilient spring for offsetting the load to be received by member 97a.
U.S. Pat. Nos. 2,739,806 and 4,273,205 disclose balances that utilize a torsion bar member as part of the balance. In these two devices, however, the torsion bar is not combined with a parallelogram linkage or with a capacitance transducer.